Relay system



Feb. 4, 1930. J. STOECKLIN ET AL RELAY SYSTEM Filed May 28, 1937 M5655:@QMM Patented Feb. 4 1939 UNITED STATES PATENT QFFICE JOSEF STOECKLIN,OF ZURICH, SWITZERLAND, AND ARNOLD BOTH, OF BRON, NEAR LYON, FRANCE,ASSIGNORS TO AKTIENG-ESELLSGl-IAFT BROWN BOVER-I & CIE., OF

BADEN, SWITZERLAND, A COMPANY OF RELAY Application filed May 28, 1927,Serial No.

Our invention relates to relay systems, and it has particular relationto systems employing impedance responsive relays or like instruments,that is, instruments that act in response to the differential action ofthe current and voltage of the line wi h which they are'associated.Relays of this typeare described in the co-pending application of JosefStoecklin, Serial No. 1 17,7591, filed November 11, 126.

In systems of the above described character, the circuit breakers at thevarious substations are provided with relays arranged to vary thetripping time of the circuit breakers in accordance with the impedanceof the line to the point where a faultoccurred. This causes the circuitbreaker nearest to the fault to open first, and thus to disconnect onlythe faulty sections from the remainder of the system.

Among the objects of the present invention is the provision of animproved relay system of the foregoing character, utilizing improvedmeans for compensating for the difference of the transformation ratio ofthe transformers energizing such relays at the various points of thesystem in order to secure definite relationship between the operatingcharacteristics of the relay devices at the several points of thesystem. fore particularly, our invention is directed to the compensationor correction of the difference in the transformation ratios of thetransformers supplying the relays of the various points of the system byadjustment of the voltage applied to the voltage element of such relays.

Our invention will be best understood from the accompanying drawingswherein:

Fig. 1 is a circuit diagram of a distribution system to which ourinvention is applicable;

Fig. 2 is a diagram similar to Fig. 1, illustrating arelay systemembodying our invention; and

Fig. 3 is an enlarged circuit diagram of the compensating transformershown in Fig. 2.

A distribution system of the type referred to hereinabove is showndiagrammatically SWITZERLAND SYSTEM 194579 17, and in Germany March 6,1926.

in Fig. 1- of the drawing wherein at substations I, II, etc., of a longhigh-voltage transmission line 10 there are provided circuit breakers 10arranged to be tripped by means of impedance relays II. The impedancerelays II are so connected to the distribution line that, upon theoccurrence of a fault, the times within which the individual relayscause the tripping of the associated circuit breakers are proportionalto the impedance of the line between the respective circuit breaker andthe fault. In most cases, this discriminating action of the relay isobtained by means of a pair of co-operating voltage and currentelements, namely, a voltage coil 12 and a current coil 13. The voltagecoil 12 is supplied through a voltage transformer 15 with a currentcorresponding to the voltage of the line at said point. The current coil13 is supplied through a current transformer 16 by a currentcorresponding to the line current at said point of the system. Bysuitably bringing into co-operation the voltage coil and current coil,12 and 13 of the relay, its action may be made dependent on the ratio ofthe voltage to the current of the line, that is, to its impedance.

In any practical system of the foregoing character the voltage andcurrent coils of the relay are not directly connected to the linebutthrough the intermediary of suitable voltage and currenttransformers, since it is impractical and also dangerous to operate therelays directly from the high voltage system.

The current and voltage transformers utilized for supplying such relaysserve very often a variety of additional purposes, such as for thecontrol of the circuit breakers in response to other characteristics ofthe system, for the supply of various meters at the substation, etc.Very often the voltage and current transformers at the various points ofthe distribution system have different transformation ratios.Accordingly, if the relays at the several substations were directlyconnected to the secondaries of the voltage and current transformers atthe different sub stations, the relays would not respond to the actualresistance of the line in the same manner. For instance, if onesubstation, say substation I, has a current transformer 16 with thetransformation ratio 100 to 5, and the current transformer at the othersubstation II has a transformation ratio 200 to 5, and the voltagetransformers at the two substations have the same transformation ratio,the action of the relays at the two substations would not be correlatedin the way required in order to secure proper discriminative action, asexplained hereinabove. Only if the current and voltage transformers atthe substations all have the same transformation ratio, the relays atthe several points of the system will exercise the same discriminativeaction.

In order to secure correlated discriminative effect with relays suppliedfrom instrument transformers that differ in their transformation ratio,special auxiliary or compensating transformers are provided, such asshown in Fig. 1 at substation II, where th compensating transformer 21is connected between the current transformer 16 and the current coil 13of the impedance relay. The transformation ratio of the compensatingtransformer 21 is so chosen with respect to the transformation ratio ofthe transformer16 that the total transformation ratio obt .ined byconnecting the two transformers in the series is again 100 to 5, like inthe current transformer at substation I. In other words, the auxiliarycurrent transformer 21 serves to compensate for the highertransformation ratio of the current transformer at substation II, asagainst other substations of the system. The compensation for thedifferences of the transformation at the various stations could also beeffected by providing auxiliary tappings on the current transformers inorder to assure that the ratios of the current and voltage supplied tothe relays at the several substations reflect the impedance of thesystem in the same way. Lack of such compensation would distort therelationship between the tripping times of the relays of the severalsubstations.

The above described arrangements for correcting for the differenttransformation ratios of the instrument transformers at the severalsubstations, have certain disadvantages, from the view point of thepractical op-' eration of such systems. Thus, when an 2111?;- iliarycurrent transformer is used, its seconary current increases with anincrease of the ratio of the main current transformer. For example, ifthe main current transformer at the first substation has a ratio of 100to 5, the normal current supplied to the current coil of the'relay willbe 5 amperes. If now at another substation the current transformer has aratio of 200 to 5, the auxiliary correcting transformer must have aratio of to 10. Under such conditions, the normal current supplied bythe current coil of the relay from the secondary winding of thecompensating transformer, will be 10 amperes. The relay will thus beoverloaded under normal working conditions as compared to a relay thatis operated with a current transformer having a 100 to 5 ratio. -heother type of compensation, by means of auxiliary taps on the currenttransformer, is not practicable because the limited number of turns usedon the current transformers makes it difiicult to obtain thereby closegraduation of the transformation ratios.

A distinct feature of the present invention resides in the utilizationof the voltage circuit of the relay for correcting discrepancies in thetransformation ratios of the current transformer supplying the relays.More generally our invention contemplates the confining of theadjustment or corrections in the transformation ratio of the instrumenttransformers supplying the relays to the voltage circuit'of such relays,irrespective of whether the correction is required by reason of improperratio of the current transformer or of the voltage transformer.

Thus, taking the example considered above of a substation, indicated inFig. 2, where the current transformer has transformation ratio of 200 to5, and we desire to compensate this ratio with respect to a substation,utilizing a current transformer having a ratio 100 to 5, we connect thecurrent coil 13 of the relay directly to the 200 to 5, currenttransformer. The correction is secured by reducing the voltage suppliedto the voltage coil 12 of the relay, in the same ratio. as the currentsupplied to the current coil 13 is reduced, as by means of an auxiliarycompensating transformer 25 connected between the voltage coil 12 andthe voltage transformer 15 of the substation. Assuming, for instance,that the secondary voltage of the voltage transformer at substation I is110 volts, the compensating transformer 25 is adjusted so that thevoltage supplied to the voltage coil. 12 of the impedance relay is only55 volts, corresponding to the higher rate of current trans formation atsaid substation.

The arrangements for applying to the voltage coil 12 of the impedancerelay only a fraction of the voltage derived from the secondary windingof the voltage transformer 15 may have a variety of forms familiar tothose skilled in the art. In the preferred construction we utilize anauto transformer, such as shown in detail in Fig.

'3. The relay that is to be used on the systern is designed so as tooperate satisfactorily when supplied directly from such currenttransformer of the ystem as has the lowest transformation ratio, withthe normal voltage, say 110 volts, applied to the voltage coil. Undersuch conditions, the relays are suitable for operation with transformershaving higher transformation ratios, it being only required to include asuitable correcting transformer in the voltage circuit of the relay toreduce the voltage applied to the voltage coil, as explained above.

In the preferred construction of the compensating transformer, shown inFig. 3, we provide a large number of taps graduated in accordance withthe decimal system to permit the tapping of as many per cent of thetotal voltage of the transformer as desired. Starting from the tapmarked 0, at an intermediate point of the Winding, there are taps to 90on one side of the transformer and taps 1 to 10 on the other side of thetransformer. Such arrangement greatly facilitates adjustment of thesensitiveness at the various stations of the system by merely varying inthe same ratio the voltage supplied to the voltage coils of the relaysat all stations,

The foregoing system for compensating differences in the transformationratios of the instrument transformers, secures correct operation of therelays independently of the differences in the instrument transformersused at the several stations; eliminates the possibility of overloadingthe relays by reason of the employment ofhigher ratio currenttransformers; and readily permits adjust-ments of the sensitiveness ofthe relays throughout the system.

l Ve claim as our invention:

1. In a distribution system, a relay device having current and voltageelements cooperating to produce an effect responsive to a ratio of thevoltage and current of said system, a circuit including a currenttransformer for supplying said main current element, a circuit includinga main voltage transformer for supplying said voltage element, and asecond voltage transformer connected between said main voltagetransformer and said voltage element to so vary the current suppliedthereto as to cause said relay device to respond to the conditions ofsaid system With a predetermined sensitiveness irrespective of thetransformation ratios of the main current and voltage transformerssupplying said relay device.

2. In a distribution system having a plurality of station, a pluralityof relay devices at said stations, each relay device comprising avoltage element and a current element cooperating in response to a ratioof the voltage and current of said system, voltage transformers at saidstations for supplying the voltage elements of said relays, currenttransformers at said stations for supplying the current elements of saidrelays, the transformation ratios of the current transformers at theseveral stations varying with respect to each other, and meansassociated exclusive ly With circuits of said voltage elements forcompensating the difierences in the transfor mation ratios of saidtransformers at the difierent stations to secure the same character ofresponse of the relay devices at the several stations.

3. The combination as defined by the claim 2, characterized by anauxiliary voltage transformer for adjusting the voltage applied to thevoltage element of said relay devices, said voltage transformer having aplurality of tappings permitting application of any desired integerpercentage of the full voltage of the voltage transformer to the voltageelement of said relay devices.

4. In a distribution system, a plurality of relay devices, each having acurrent element and a voltage element cooperating to produce an effectcorresponding to a predetermined relation of the current and voltage ofa system, a plurality of current transformers of differenttransformation ratios for supplying the current elements of theindividual relay devices, and a plurality of voltage transformer meansassociated With the individual relay devices for supplying the voltageelements of said devices, said voltage transformer means havingdifferent transformation ratios so related to the different transformation ratios of said current transformers, as to secure saidpredetermined relation of the current and voltage of the system in saidrelay devices.

5. In a distribution system, an alternating current transmission line, aplurality of circuit breakers at spaced points along said line, aplurality of relay means for individually operating said circuitbreakers, said relay means having current elements and voltage elementsoperating in response to a predetermined relationship of the current andvoltage of said line, current transformers of different transformationratios for individually supplying the current elements of said relays,and voltage transformer means of different transformation ratios forindividually supplying the voltage elements of said relays, the voltagetransformation ratios being so adjusted to the transformation ratios ofthe associated current transformers as to secure the predeterminedrelation of line current and line voltage in the individual relays.

6. In a distribution system, an alternating current transmission line, aplurality of circuit breakers at spaced points along said line, aplurality of relay means for individually operating said circuitbreakers, said relay means having current elements and voltage elementsoperating in response to a predetermined relationship of the current andvoltage of said line, current transformers of different transformationratios for individually supplying the current elements of said relays,main voltage transformers of different transformation ratios forindividually supplying the voltage elements of said relays, the voltagetransformation ratios being so adjusted to the transformation ratios ofthe :asso'ciated :currentttransformers as to secure the predeterminedrelation of line current and 'line voltage in the individual relays, andadditional voltage transformer means interposed between one of said mainvoltage transformers and the voltage element of the associated relay forcompensating for the (li iference'of'the transformation ratio of theassociated current transformer against that of aitransformerassociatedwith another relay.

In testimony whereo'fI-have hereunto subscribed my name this Gth'day ofSeptember, A. D. 1927, at Zurich, Switzerland.

J OSEF STOECKLIN.

In testimony whereof I have hereunto subscribed my name this 27th day ofOctober, 'A. D. 1927, :at Lyon, France.

ARNOLD ROTH.

